Catálogo de publicaciones - revistas

<jats:title>All Together Now</jats:title> <jats:p> In the social amoeba <jats:italic>Dictyostelium discoideum</jats:italic> , periodic synthesis and release of cyclic AMP (cAMP) guides the cellular aggregation required to form fruiting bodies. It has been unclear whether the initiation of this behavior is owing to synchronization of autonomously oscillating cells or whether individual cells remain nonoscillatory unless the entire population becomes oscillatory. <jats:bold> Gregor <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1021" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1183415">1021</jats:related-article> , published online 22 April; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5981" page="987" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1190372">Prindle and Hasty</jats:related-article> </jats:bold> ) used live-cell imaging to show that cAMP pulses originate from a specific location in space and that individual cells move in and out of these signaling centers. The observations suggest that oscillations do not originate from autonomous activities of specialized cells. However, individual cells do display stochastic cAMP-pulsing below a threshold external concentration of cAMP, and the generation of synchronized oscillations could only be modeled accurately when this random pulsing was taken into account. </jats:p>

<jats:title>Complex SAGA</jats:title> <jats:p> The SAGA (Spt-Ada-Gcn5-Acetyltransferase) complex, which is conserved in eukaryotes, plays a key role in regulating gene expression. It is comprised of 21 proteins, and its functions include histone acetylation and deubiquitination. <jats:bold> Samara <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1025" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1190049">1025</jats:related-article> , published online 15 April) now report the structure of the SAGA deubiquitinating module (DUBm), a four-protein subcomplex, both on its own and bound to ubiquitin aldehyde. The domains are interconnected and stabilized by eight zinc atoms. The organization gives insight into why DUBm complex formation is required to activate the catalytic domain of the enzyme and suggests how DUBm might bind to monoubiquitinated histones. </jats:p>

<jats:title>Network for Recovery</jats:title> <jats:p> A long-standing theory suggests that social diversity leads to economic development. By combining the United Kingdom's telephone communication records (both landline and mobile) with information on regional economic conditions, <jats:bold> Eagle <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1029" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1186605">1029</jats:related-article> ) demonstrate that network diversity alone accounts for over three-quarters of the variance of a region's economic status. Although the data cannot be used to show causality, the association suggests that economic development and recovery may depend not solely on monetary stimulus but also on the development of a nation's social infrastructure. </jats:p>

<jats:title>Penetrating Attack on Tumors</jats:title> <jats:p> While considerable research effort in oncology is focused on the design of new cancer drugs, an important but relatively understudied research area is the development of methods that optimize the delivery and tumor penetration of existing cancer drugs. Previous work has characterized a peptide (iRGD) that selectively targets and penetrates tumor tissue by virtue of its specific interaction with tumor blood vessels. Now, studying mouse models, <jats:bold> Sugahara <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1031" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1183057">1031</jats:related-article> , see the cover) show that coinjection of the iRGD peptide increases the tumor penetration and antitumor activity of several cancer drugs, including the cytotoxic agent doxorubicin and the therapeutic antibody trastuzumab (Herceptin), without increasing their harmful effects on healthy tissue. Importantly, these effects did not require chemical conjugation of the cancer drugs to the peptide. </jats:p>

<jats:title>Subtle Variation</jats:title> <jats:p> Despite vast phenotypic differences, vertebrates have many readily recognizable specific cell types, like liver hepatocytes. The gene expression that defines specific cells depends on evolutionarily conserved orthologous transcription factors. <jats:bold> Schmidt <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1036" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1186176">1036</jats:related-article> , published online 8 April) studied the conservation and divergence in the genome-wide binding of two such transcription factors, CEBPA and HNF4A, in livers from human, dog, mouse, short-tailed opossum, and chicken. Although the sequence bound by orthologous transcription factors was similar, the vast majority of binding events were unique to each species. </jats:p>

<jats:title> Cytosol, <jats:italic>Salmonella</jats:italic> , and pH </jats:title> <jats:p> <jats:italic>Salmonella</jats:italic> and other bacterial pathogens grow inside animal host cells within intracellular vacuoles. The bacteria secrete effector proteins across the vacuole membrane, altering the host-cell physiology to the pathogen's advantage. The secretion process involves a specialized secretory apparatus, the type III secretion system, whose assembly is triggered by the low pH within the host-cell vacuole. Now, <jats:bold> Yu <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1040" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1189000">1040</jats:related-article> , published online 15 April; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5981" page="981" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1190758">Collier</jats:related-article> </jats:bold> ) have identified neutral pH as a physiological signal for effector translocation by intracellular <jats:italic>Salmonella</jats:italic> . The process involves the disassembly of a membrane-bound regulatory complex that is also found in other animal pathogens. Thus, <jats:italic>Salmonella</jats:italic> exploits the low pH of the vacuole as a signal to induce assembly of the secretion system, and then the neutral pH of the cytoplasm to trigger effector translocation. </jats:p>

<jats:title>Budding Yeast Kinome Revealed</jats:title> <jats:p> Covalent modification of proteins by phosphorylation is a primary means by which cells control the biochemical activities and functions of proteins. To better understand the full spectrum of cellular control mechanisms mediated by phosphorylation, <jats:bold> Breitkreutz <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1043" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1176495">1043</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5981" page="983" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1190993"> Levy <jats:italic>et al.</jats:italic> </jats:related-article> </jats:bold> ) used mass spectrometry to identify proteins that interacted with the complete set of protein kinases from budding yeast and with other molecules, including phosphatases, which influence phosphorylation reactions. The results reveal a network of interacting protein kinases and phosphatases, and analysis of other interacting proteins suggests previously undiscovered roles for many of these enzymes. </jats:p>

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